The Supreme Court decided on Monday to review President Obama’s 2010 health-care overhaul, promising a high-profile hearing on the question dominating American politics: the constitutional limits of the federal government’s power.

No initiative has exemplified Obama’s progressive domestic agenda or inflamed his conservative opponents like the Patient Protection and Affordable Care Act. The Republican presidential candidates have taken an oath to dismantle what they derisively call Obamacare, and the court’s decision will deliver an unmistakable — if unpredictable — jolt to the political system in the midst of next year’s national elections.

Next March, around the second anniversary of the act’s passage, the nine justices will hear arguments in the case, taking on the role of constitutional referee between those who see the law as a trespass on individual and states’ rights and those who consider it an extension of a safety net to Americans regardless of where they live or work.

A ruling on whether the Constitution gives Congress the power to require nearly every American to obtain health insurance or pay a penalty will define the court under the still-new tenure of Chief Justice John G. Roberts Jr. It will probably be the court’s highest-profile decision since Bush v. Gore ended the presidential contest of 2000.

As a mark of the case’s importance, the justices said they will hear 51/2 hours of oral arguments on the constitutional question and related issues. That appears to be a modern record: In 2003, the court devoted four hours of oral arguments to the McCain-Feingold campaign finance act, a sweeping law aimed at controlling the influence of money in elections.

Even as aspects of the health-care law have been implemented, opponents and supporters have awaited the court’s decision. Oral arguments will most likely be held over one or two days, with a ruling expected before the court recesses in late June.

●Whether Congress was acting within its constitutional powers by requiring all Americans to have at least a basic form of health insurance by 2014. Those who do not will be required to pay a penalty on their 2015 income tax returns.

●Whether other parts of the law can go forward if the “individual mandate” is found unconstitutional. Lower courts have differed on the question. The administration says the law’s more popular features cannot work financially without the mandate that all Americans join the system.

●Whether Congress is improperly coercing states to expand Medicaid, the subsidized health-care program for the poor and disabled.

●Whether the issue is even ripe for deciding. Some lower-court judges have said that the penalty paid for not having insurance is the same as a tax and, under the federal Anti-Injunction Act, cannot be challenged until someone has to pay it in 2015.

White House is ‘confident’

The White House, which had called on the court to take the case now, has said that the challenges to the act are no different from those that faced Social Security, the Civil Rights Act and other major pieces of social legislation.

“We know the Affordable Care Act is constitutional and are confident the Supreme Court will agree,” said White House spokesman Dan Pfeiffer.

Senate Republican leader Mitch McConnell (Ky.) countered that polls consistently show that the legislation is unpopular. “This misguided law represents an unprecedented and unconstitutional expansion of the federal government into the daily lives of every American,” he said.

The Democratic-controlled Con­gress that passed the act said its authority was grounded in the Constitution’s granting of power to regulate interstate commerce and to pass laws “necessary and proper” to create a functioning federal government. Opponents said that power was never meant to require individuals to purchase a product — in this case, health insurance — that they do not want.

What the justices will do with the case is difficult to predict.

Most who follow the court believe that the four liberals are likely to agree that the power to “regulate commerce with foreign nations, and among the several states” naturally applies to health care, which accounts for more than 17 percent of the nation’s gross domestic product.

Justices Ruth Bader Ginsburg and Stephen G. Breyer have consistently agreed with an expansive view of the commerce clause; Justices Sonia Sotomayor and Elena Kagan have not yet considered a case that offered a substantial test.

It is more complicated on the other side of the court. Justice Clarence Thomas is the only member who has consistently voted for a limited view of the power. Justices Antonin Scalia and Anthony M. Kennedy have a more mixed record on the issue.

Conservative groups have called on Kagan to sit out the case because she worked for the Obama administration as solicitor general. Liberal groups have said Thomas faces a conflict because of the political activities of his wife.

But justices make their own decisions about whether they have reason to recuse themselves, and there was no indication from Monday’s order that either would miss the case.

Breaking the pattern

As soon as Obama signed the health-care bill, opponents raced to challenge it. The early court decisions followed a predictable pattern, with district judges appointed by Democratic presidents upholding the law and Republican appointees striking it down.

But at the appeals court level, that changed. In the 11th Circuit decisions, Judge Frank Hull, a Bill Clinton appointee, joined with a Republican colleague in saying that the “unprecedented” legislation went too far. They said that if the law were constitutional, it would be impossible to say what action on the part of the government would go too far.

At the U.S. Court of Appeals for the 6th Circuit in Cincinnati and the U.S. Court of Appeals for D.C. Circuit, two prominent Republican-appointed judges agreed that the law is intrusive but within Congress’s powers.

In Cincinnati, Judge Jeffrey Sutton, a George W. Bush appointee, was the deciding vote to uphold the act. Last week in Washington, Senior Judge Laurence Silberman, named to the bench by President Ronald Reagan, wrote an opinion saying that the question was political, not constitutional.

“It certainly is an encroachment on individual liberty,” Silberman wrote. But then — alluding to other cases in which the Supreme Court has ruled that the commerce clause gives Congress power — he added that “it is no more so than a command that restaurants or hotels are obliged to serve all customers regardless of race, that gravely ill individuals cannot use a substance their doctors described as the only effective palliative for excruciating pain, or that a farmer cannot grow enough wheat to support his own family.”

Even as the legal wrangling grows to a crescendo, some aspects of the law are already being enforced. Those include requirements that many insurance plans allow young adults to stay on their parents’ policies until age 26; cover a range of preventive services, including birth control, without imposing co-payments or other out-of-pocket costs; eliminate lifetime dollar limits on coverage; and begin phasing out annual caps.

Many insurers also are now barred from excluding children with preexisting conditions — a prohibition that will be extended to all individuals in 2014.

The three 11th Circuit cases accepted by the court are National Federation of Independent Business v. Sebelius; Florida, et al., v. Department of Health and Human Services; and Department of Health and Human Services v. Florida, et al.

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